Nonlinear structures in engineering are affected by uncertain parameters.
Firstly, the displacement when the interval variable takes the midpoint value is
obtained, and the nonlinear problem is transformed into a linear problem. Five
calculation methods of nonlinear interval finite element for general nonlinear
problems and elastoplastic problems are proposed. According to the perturbation
technique, a perturbation method is proposed. According to Taylor expansion, Taylor
expansion method is proposed. Neumann expansion, Sherman Morrison Woodbury
expansion and a new iterative method are proposed.